Selective circuit protecting device



Feb. 7, 1933. R. DUBUSC ET AL 1,896,943

SELECTIVE CIRCUIT PROTECTING DEVICE Filed April 15, 1930 3 Sheets-Sheetl Feb. 7, 1933. DUBUSC ET AL 1,896,943

SELECTIVE CIRCUIT PROTECTING DEVICE Filed April 15, 1930 3 Sheets-Sheet2 Feb. 7, 1933. R, DUBUSC ET AL 1,896,943

SELECTIVE CIRCUIT PROTECTING DEVICE Filed April 15, 1950 5 Sheets-Sheet5 F 5.7 I Inventor-.9

E fluhwc m/Zw'am [Zz'oviczi f y Haw WW 'Efibrnqys.

Patented Feb. 7, 1933 PATENT OFFICE ROGER DUBUSC AND AVBAM DAVID ILIOVICI, 01 PARIS, FRANCE, ASSIGNORS TO COM- PAGNIE POUR LA FABRICATION DESCOMPTEURS ET MATERIEL DUSINES A GAZ, OF

MONTROUGE, SEINE, FRANCE, A JOINT STOCK COMPANY OF FRANCE SELECTIVECIRCUIT PROTECTING DEVICE Application filed April 15, 1930, Serial No.444,536, and in France April 30, 1929.

Several devices based on the use of the negative or the zero phasesequence components of the currents, voltages or powers have alreadybeen proposed for protecting a circuit.

Pilot wires have likewise been used in selective protection systems andin particular the pilot wires have been used as conductors in theauxiliary circuit, the current of which flows through the trip coils ofthe circuitbreakers or intermediate relays.

The present invention is concerned with devices in which pilot wires fortransmitting the current of the auxiliary sources are used inconjunction with devices for obtaining the negative or zero phasesequence components.

By combining the pilot wires with the filter circuits for obtaining thenegative or zero phase sequence components, a more accurate and flexibleselection is obtained than when the currents or powers of the circuitsare used directly; in addition, as only direct current generally flowsthrough the pilot wires, and, moreover, only for the very short lengthof time necessary for operating the circuitbreakers, it will nearlyalways be possible to avoid designing special pilot wires, and telephonewires or any other Wires at hand may be used.

, Several embodiments of the invention have been illustrated in theaccompanying drawings in which:

Fig. 1 illustrates a protecting device for a plurality of feeders inseries.

Fig. 2 shows a protecting device for a circuit comprising feeders inparallel and groups of feeders in series.

Fig. 3 shows a protecting device which differs from that of Fig. '2 inthat the negative or zero phase sequence component of the current orpower flows in one direction only.

Figs. 4, 5, 6 and 7 illustrate further modifications of devices forprotecting electric circuits. y Y

In Fig. 1, B0 BO ,,BO Bog-designate the bus-bars of the power station orof the sub-stations; F F F are three three-phase feeders following oneafter another; D D D D' D D, the circuit-breakers of said feeders (ithas been assumed that there is one circuit-breaker at each end), butcertain of the circuit-breakers may be cut out. B B B B B B are the tripcoils of the circuit-breakers which may be replaced by auxiliary relays;fp fp fp are pilot wires through which flow the currents produced by theauxiliary sources SA SA SA F is a return wire for the currents of thepilot wires (the wire F may be replaced by the earth) RW RIV RVV arewattmetric relays (responsive to the negative or zero phase sequencecomponents of power) of the doublethrow type. In these relays 0 is thecurrent winding of the relay RVV fed by the secondaries of the threecurrent transformers t mounted in parallel; 6' is the voltage winding ofthe same relay fed by the three reactance, resistance or capacitywindings 7 7 1* The winding 6 receives the earth current (resultant ofthe currents in the three phases) and 6' a current proportional to thezero phase sequence component of the voltage. The reference characters ee t 1' 7 1" 6 6' t 1' 1" 7" have the same meaning in connection with therelays RVV and Rl/V as the corresponding preceding reference characters.

The wattmetric relays are so arranged that the contact of each relaywill close to the left 1 (at 1) when the negative or zero phase sequencecomponent of the power, according to the case in point, in thecorresponding feeder is directed towards the right.

In order to make the operation of the device readily understandable, itwill be assumed that there is an earth fault at M; it will likewise beassumed that the relays RW RW are earth relays and that there are atleast two earths, one at T and the' other at T It is known that the zerophase sequence power component is always directed from the faulty pointtowards the earths: hence it will have the direction of the arrows f inthe feeder F 1 and in that portion of the feeder F which lies to theleft of the point M, and the opposite direction (arrows f) to the rightof M. The consequence is that the contacts of the relays RW and RW willclose to the right (at 2) whereas the contacts of the relays RW and RVVwill close to the left '(at 1). It will be readily understood that thecircuit of the auxiliary source 8A is closed, which will cause thecircuit-breakers B ,]3 to trip, while the circuits of the sources SA andSA will remain open.

Fig. 2 shows the diagram of the same device as that of Fig. lapplied tothe more complex 10 case of a circuit comprising feeders in parallel andgroups of feeders in series. In this and in the following figures, inorder to avoid overcrowding, the coils of the relays have not beenillustrated but they are of course the same as those shown in Fig. 1. vOnly one wire of each feeder has been illustrated, and it has beenassumed that there are two earths at T and T The feeders F F FQare inparallel; the feeders F and F 2 are'independent; the first is continuedby two independent feeders F and F The feeder F is continued by twofeeders F and F in parallel. As in Fig. 1, fp fp illustrate pilot wireswhich transmit the currents of the auxiliary sources SA SA the latterare not placed, as in Fig. 1, in the pilot wires, but inthe wires whichconnect the points common to they movable contacts of the relays f tothe common return wire F; the other refer- 0 ence characters have thesame meaning as in Fig. 1;. The advantage of locating the aux- 'iliarysources in the manner shown is that their number is reduced. It will beobserved furthermore that only one auxiliary source is used for twosub-stations. Obviously, one source could be used for each station, eachsource would then only furnish half the voltage to be provided in thecase of Fig. 2.

If batteries are used, the number of units 40 for the whole network isthe same whether one source per station or one source per two stationsbe used. It will be observed that there are two circuit-breakers perfeeder and two wattmetric relays, save in th case of the feeders F andF' where one circuit-breaker and one relay per feeder has been provided.

For the latter feeder, two relays with one ortwo circuit breakers, ortwo circuit-breakers with a single relay might have been used. Inreality, there is one relay such as RW for two feeders having a commonend. 7 The current coil of this relay may be fed with the current of theone feeder or the other; practically, there will be preferably one relayfor each end of each feeder, as will be seen in Fig. 7.

To understand the operation of the device, it will be assumed in thefirst place that a fault occurs at A, then that the fault is at B,finally at O. 1

If the fault be at A, the zero phase sequence power component fiowsinboth directions in the feeder F and in one direction only in alltheother feeders. From what has been seen in the case of Fig. 1, the relayIWV will close its contact at 2, while the contact of the relay RW willclose at 1. The current from the source SA will pass through the windsings B and 13" and the oircuit-breakers D and D 2 will trip. On theother hand, in the other feeders, the contacts of the relayscorresponding to the same feeder will close to the same side and thecircuits of the corresponding pilot wires will remain open. If thefaultoccur at B, on the feeder F the same conditions will obtain for thisfeeder as for the feeder F in the preceding case and the twocircuit-breakers between which it is confined will trip.

If the fault occur at O, the zero phase sequence power component to theright of G will be nil while'in the portion of the feeder F -situated tothe left of C, the power will be directed towards the left and thecircuitbreaker D will trip. In the feeder F the zero phase sequencepower component will be nilbecause this feeder includes no earth;consequently its relay RW will remain open. Were there an earth at theright endof this feeder, the power flowing through it would go towardsthe earth and 'wattmetric relay Rl V would deflect to 1 while the pilotwire p 'would always remain open. Similar results would be obtained withnegative phase sequence power components, whether'the neutral ofthefeeders be insulated or earthed, the fault occurring between twowires in the first case and between twowires or with the earth in thelatter case.

Fig. 3 illustrates the circuit arrangement corresponding to the case inwhich the zero phase sequence current or power component only proceedsin one direction; this would be the case should-only one earthobtain forexample at T. In the case of a fault at a point M, the zero phasesequence current component only exists to the leftof M and the zerophase sequence power component proceeds from M to T.

In lines in which the neutral is earthed, and assuming that there is acontact between two wires at M, similar conditions to the preceding onesfor the negative phase sequencecurrent or power component will prevail,if the line be open to the right of the fault, so that 'llO in thisportion, there will be neither generators nor receivers (infiniteimpedance withrespect to the negative phase sequence current component).7

In Fig. 3, it has been assumedthat the relays are responsive to the zerophase se quence component and that there is a single earth at T. Thevarious reference characters have the same meaning as in Figs. 1 and 2but the relays RW RW may be Wattmetric or current relays. V

In the former case, they must deflect to the right when the powerproceeds to the left. In the latter case, the flow of current throughthe relay must make'the latter deflect to the each feeder two pilotwires right. It will be observed that the relays are normally closed tothe left (at 1) If a fault occur at a point, the current flows throughthe feeders, or feeder sections lying on the left of the fault (betweenthe faulty point and the earth) and does not flow through the others.Thus, for example, if the fault occur at M, the current only flows in.the relay RIV which deflects to the right and closes the circuit of thewindings B B while the other auxiliary circuits remain open. If thefault occur at M onthe feeder F the relays nw RIV deflect to the right,and it will be readily seen that only the circuit of the winding B" isclosed.

Figs. 4 and5 show circuit arrangements in which it has been assumed thatthe negative or zero phase sequence power component may proceed now inone direction, now in the other, now in both simultaneously, thiscorresponds to the most general case of a network operating underchanging working conditions.

The case of a network with earthed neutral in which the position of theearths is variable will be considered.

In the two figures, there are associated with fl fp i F 7 fp fp fp and areturn wire F which may be replaced by the earth. In Fig. 4, it isassumed that the coils of the circuit-breakers have a double winding orthat the circuitbreakers have two coils. In Fig. 5, the circuit breakersB B have single windings, but intermediate relays A A A A grouped inpairs with their lel are utilized.

In both figures, the reference letters h ve the same meaning as in thepreceding figures; in addition, in Fig. 5, A A A r 22 designate theintermediate relays having con tacts C C C C It will be observedmoreover that in Fig. 4, there is one auxiliary source for twostations,whereasin Fig. 5 there is one source per station.

The operation of the device is readily understandable. If, in thecircuit arrangement of Fig. 4, a fault occur at a. point M, three casespresent themselves: 1. If there be only one earth at the left end, thecontacts of the relays RIV and RWV will close at 2, whereas thepositions of the contacs of the other relays will remain unchanged; itwill be seen that in this case, only the circuit of the coils B and B isclosed, whereby the circuit-breakers D;. and D will trip; 2. The earthis at the right end; in this case, the current only flows to the rightof M and the relays RI and RW', close their contacts to the left; itwill be seen that only the circuit of the windings B and B is closed; 3.Earths exist at both ends; in this case, the relays RVV RI RVV and Rid"close their contacts to the right, while the o h-ers close theircontacts to the left (here all the relays contacts in paralare assumedto'be wattmetric and to deflect to the left if the power goes to theright) it will be seen that only the circuits of the windings B B and BB are closed; hence the same circuit-breakers as in the preceding caseswill trip.

In the case of Fig. 5, the same three cases have to be considered, buthere the closing of the circuits fp or fp will cause the current to flowin the windings A A A A of the intermediate relays, thus closing thecontacts (1' (3'2 C3, C which will cause the current to pass through thewindings B and B If there be only one auxiliary source for all thestations, an additional pilot wire must beused so that the two poles ofthe source may be ut lized at each station. Fig. 6 illustrates a c rcuitarrangement similar to that of Fig. 4 save that only one auxiliaryso'urce SA obtains. The reference letters have the same meaning as inFig. 4, but there obiains in addition the wire F which in conjunctionwith the wire F enables the two poles of the source to be usedthroughout.

In the preceding devices, it has been assumed that each of thewattmef'ric relays save those at the ends, serves to protect two feedersstarting from the same bus-bars. Thus, the relay RVV of Fig. 1 servesfor the feeders F and F similarly, the relay RIV of F 2 serves for thefeeders F and F Th s arrangement which is economical may become faultyand it is preferable that each wattmetric relay should only serve for agiven feeder. Moreover, in the more general types of protective devices,such as those corresponding to the circuit arrangements of Figs. 4 and5, at each feeder end, a single wattmeric relay having a centrallypositioned double contact and two auxiliary relays with contacts pressedagainst their stops may be used instead of two wattmetric relays withcontacts pressed against their stops.

F g. 7 illustrates a circuit arrangement similar to that of Fig. 5 inwhich the feeders are protected independently of one another withwattmetric and auxiliary relays.

In this figure, D D illustrate the cir (nit-breakers mounted in thefeeders F F F 3 B B the coils of the circuit-breakers: fp fp the pilotwires, FF the common return wire or the earth; RWV RIV wattmetric relayswith two contacts 1 and 9.; RA RA HA auxiliary relays. The relays HA HARA have their contacts thrown over against the lefthand stops anddeflect to the right when current flows, while therelays RA RA RA havetheir contacts thrown over against the righthand stops and deflect tothe left when current flows through their windings.

The relays RW RW close the contact 1 when the zero or negative phasesequence powercomponent is directed tothe of operation of the device isf is directed to the left in the feeder F and in of a plurality'of theportion of the feeder F lying to the left of M, while no power passes tothe right of M. The relaysRW and RW close their contacts 2, so that thecontacts of the auxiliary relays RA and HA move over to 2 and the pilotwires fp and fp remain open. Similarly, the pilot wires fp and fp remainopen because the relays RW and RW do not act. On the other hand, therelay RN' deflecting to the right closes the contact of vR-A at 2,whereby the circuit of the pilot wire fp is closed and current passesthrough the windings B and B thus causing the circuit-breakers D and Dto trip.

It will be seen similarly that if the earth is at T it is the pilot wirefp which is closed; if the two earths T and T exist simultanenously, thetwo pilot wires fp and In the various devices indicates, the relays maybe instantaneous. However, in practice it will be preferable slightly toretard certain of the relays so as to avoid untimely operation. 7

If watmetric or curren relays are used alone, they will be slightlyretarded. When using auxiliary relays, only the latter might beretarded. In all the devices, the windings B B 13 may be windings ofintermediate or auxiliary relays acting on the windings of thecircuit-breakers.

We claim: Y

1. In a selective protective system for an alternating current network,the combination relays, means for rendering said relays responsive tothe negative or zero symmetrical phase sequence component of the poweror current of said network, a plurality of circuit-breakers mounted insaid alternating current network and including trip coils, auxiliarysources of current, a plurality of auxiliary relays, pilot wires adaptedto convey current from said auxiliary sources both to said trip coilsand to said auxiliary relays, and two sets of switch means operated bysaid'iirst mentioned relays and said auxiliary relays respectively forclosing circuits for said auxiliary relays and trip coils respectivelythrough said pilot wires.

2. In a selective protective system for an alternating current network,the comblnationof a plurality of relays, means for rendering said relaysresponsive to the negative Let a fault occur current, a plurality ofauxiliary relays, two

pilot wires for each feeder adapted to convey current from saidauxiliary source both to said trip coils and to said auxiliary relays, V

and two sets of switch means operated by said first mentioned relays andsaid auxiliary relays respectively for closing circuits for saidauxiliary relays and trip coils respectively through said pilot wires. 1Y

3. In a selective protective system for an alternating current net-work,including a plurality of feeders, the combination of a plurality ofrelays, one at each end of each feeder, means for rendering said relaysresponsive to the negative or zero phase sequence component of thecurrent flowing in each feeder, or of the'tension between two feeders, aplurality of circuit breakers mounted in said alternating currentnet-work and including trip coils, auxiliary sources of current, a pilotwire for each feeder adapted to convey the current of said auxiliarysource to said tripcoils, and means controlled by said relays for makingor-breaking the circuits of said trip coils through said auxiliarysources depending onthe direction of the phase sequence component ofthecurrent or tension influencing the relays.

a. In a selective protective system for an alternating current net-work,including a plurality of feeders, the combination of a plurality ofrelays, one at each end of each feeder, means for rendering said relaysresponsive to the negative or zero phase sequence component of thecurrent flowing in each feeder, or of the tension between two feeders,auxiliary sources of current, a plurality of circuit breakers mounted insaid alternating current net-work and including trip coils, pilot wiresconnecting said trip coils to said auxiliary current sources and two-wayacting contact makers operated by said relays respectively in onedirection or the other depending on the direction of the symmetricalphase sequence componentof the current or tension influencing saidrelays, for making or breaking the circuits of said trip coils throughsaid auxiliary sources.

' ROGER DUBUSC.

AVRAM DAVID ILIOVIOI.

